Final answer:
Cumulative learning is the feature described in the question, where students build their skills from sounds to words to sentences to text with a high percentage of words that have been taught.
Step-by-step explanation:
The feature described in the question, skill building from sounds to words to sentences to text with a high percentage of words that have been taught, is cumulative learning. Cumulative learning refers to a method where new skills and knowledge are built upon previous ones, using a step-by-step approach. In this case, students start by learning individual sounds, then progress to forming words, sentences, and ultimately reading entire texts. This approach ensures that students continuously reinforce and expand their understanding of the material they have learned.